One of the most prevalent joint problems is back pain, particularly in the “small of the back” or lumbosacral (L4-S1) region. In many cases, the pain severely limits a person's functional ability and quality of life. Such pain can result from a variety of spinal pathologies. Through disease or injury, the vertebral bodies, intervertebral discs, laminae, spinous process, articular processes, or facets of one or more spinal vertebrae can become damaged, such that the vertebrae no longer articulate or properly align with each other. This can result in an undesired anatomy, loss of mobility, and pain or discomfort. Duke University Medical Center researchers found that patients suffering from back pain in the United States consume more than $90 billion annually in health care expenses, with approximately $26 billion being directly attributable to treatment. Additionally, there is a substantial impact on the productivity of workers as a result of lost work days. Similar trends have also been observed in the United Kingdom and other countries. As a result of this problem, increased funding is being applied toward developing better and less invasive orthopedic intervention devices and procedures.
Over the years the increased funding has led to the development of various orthopedic interventions. These include interventions suitable for fixing the spine and/or sacral bone adjacent the vertebra, as well as attaching devices used for fixation, including: U.S. Pat. No. 6,290,703, to Ganem, for Device for Fixing the Sacral Bone to Adjacent Vertebrae During Osteosynthesis of the Backbone; U.S. Pat. No. 6,547,790, to Harkey, I I I, et al., for Orthopaedic Rod/Plate Locking Mechanisms and Surgical Methods; U.S. Pat. No. 6,074,391, to Metz-Stavenhagen, et al., for Receiving Part for a Retaining Component of a Vertebral Column Implant; U.S. Pat. No. 5,891,145, to Morrison, et al., for Multi-Axial Screw; U.S. Pat. No. 6,090,111, to Nichols, for Device for Securing Spinal Rods; U.S. Pat. No. 6,451,021, to Ralph, et al., for Polyaxial Pedicle Screw Having a Rotating Locking Element; U.S. Pat. No. 5,683,392, to Richelsoph, et al., for Multi-Planar Locking Mechanism for Bone Fixation; U.S. Pat. No. 5,863,293, to Richelsoph, for Spinal Implant Fixation Assembly; U.S. Pat. No. 5,964,760, to Richelsoph, for Spinal Implant Fixation Assembly; U.S. Pat. No. 6,010,503, to Richelsoph, et al., for Locking Mechanism; U.S. Pat. No. 6,019,759, to Rogozinski, for Multi-Directional Fasteners or Attachment Devices for Spinal Implant Elements; U.S. Pat. No. 6,540,749, to Schafer, et al., for Bone Screw; U.S. Pat. No. 6,077,262, to Schlapfer, for Posterior Spinal Implant; U.S. Pat. No. 6,248,105, to Schlapfer, et al., for Device for Connecting a Longitudinal Support with a Pedicle Screw; U.S. Pat. No. 6,524,315, to Selvitelli, et al., for Orthopaedic Rod/Plate Locking Mechanism; U.S. Pat. No. 5,797,911, to Sherman, et al., for Multi-Axial Bone Screw Assembly; U.S. Pat. No. 5,879,350, to Sherman, et al., for Multi-Axial Bone Screw Assembly; U.S. Pat. No. 5,885,285, to Simonson, For Spinal Implant Connection Assembly; U.S. Pat. No. 5,643,263, to Simonson for Spinal Implant Connection Assembly; U.S. Pat. No. 6,565,565, to Yuan, et al., for Device for Securing Spinal Rods; U.S. Pat. No. 5,725,527, to Biederman, et al., for Anchoring Member; U.S. Pat. No. 6,471,705, to Biederman, et al., for Bone Screw; U.S. Pat. No. 5,575,792, to Errico, et al., for Extending Hook and Polyaxial Coupling Element Device for Use with Top Loading Rod Fixation Devices; U.S. Pat. No. 5,688,274, to Errico, et al., for Spinal Implant Device having a Single Central Rod and Claw Hooks; U.S. Pat. No. 5,690,630, to Errico, et al., for Polyaxial Pedicle Screw; U.S. Pat. No. 6,022,350, to Ganem, for Bone Fixing Device, in Particular for Fixing to the Sacrum during Osteosynthesis of the Backbone; U.S. Pat. No. 4,805,602, to Puno, et al., for Transpedicular Screw and Rod System; U.S. Pat. No. 5,474,555, to Puno, et al., for Spinal Implant System; U.S. Pat. No. 4,611,581, to Steffee, for Apparatus for Straightening Spinal Columns; U.S. Pat. No. 5,129,900, to Asher, et al., for Spinal Column Retaining Method and Apparatus; U.S. Pat. No. 5,741,255, to Krag, et al., for Spinal Column Retaining Apparatus; U.S. Pat. No. 6,132,430, to Wagner, for Spinal Fixation System; U.S. Pat. No. 7,780,703, and to Yuan, et al., for Device for Securing Spinal Rods.
Another type of orthopedic intervention is the spinal treatment decompressive laminectomy. Where spinal stenosis (or other spinal pathology) results in a narrowing of the spinal canal and/or the intervertebral foramen (through which the spinal nerves exit the spine), and neural impingement, compression and/or pain results, the tissue(s) (hard and/or soft tissues) causing the narrowing may need to be resected and/or removed. A procedure which involves excision of part or all of the laminae and other tissues to relieve compression of nerves is called a decompressive laminectomy. See, for example, U.S. Pat. No. 5,019,081, to Watanabe, for Laminectomy Surgical Process; U.S. Pat. No. 5,000,165, to Watanabe, for Lumbar Spine Rod Fixation System; and U.S. Pat. No. 4,210,317, to Spann, et al., for Apparatus for Supporting and Positioning the Arm and Shoulder. Depending upon the extent of the decompression, the removal of support structures such as the facet joints and/or connective tissues (either because these tissues are connected to removed structures or are resected to access the surgical site) may result in instability of the spine, necessitating some form of supplemental support such as spinal fusion, discussed above.
Other orthopedic interventional techniques and processes have also been developed to treat various spinal and joint pathologies. For example, U.S. Pat. No. 6,726,691 to Osorio for Methods and devices for treating fractured and/or diseased bone; U.S. Pat. No. 7,155,307 to Scribner for Systems and methods for placing materials into bone; U.S. Pat. No. 7,241,303 to Reiss for Devices and methods using an expandable body with internal restraint for compressing cancellous bone; and U.S. Patent Pubs. 2005/0240193 to Layne for Devices for creating voids in interior body regions and related methods; 2006/0149136 to Seto for Elongating balloon device and method for soft tissue expansion; 2007/0067034 to Chirico for Implantable Devices and Methods for Treating Micro-Architecture Deterioration of Bone Tissue; 2006/0264952 to Nelson for Methods of Using Minimally Invasive Actuable Bone Fixation Devices.
Health care providers rely on an understanding of joint anatomy and mechanics when evaluating a subject's suspected joint problem and/or biomechanical performance issue. Understanding anatomy and joint biomechanics assists in the diagnosis and evaluation of a subject for an orthopedic intervention. However, currently available diagnostic tools are limited in the level of detail and analysis that can be achieved. Typically, when treating joint problems, the intention is to address a specific structural or mechanical problem within the joint. For example, a surgeon might prescribe a spinal fusion procedure to physically immobilize the vertebra of a subject suffering from vertebral instability, or a physical therapist might prescribe exercises to strengthen a specific tendon or muscle that is responsible for a joint problem, etc.
It follows, therefore, that the extent to which a specific treatable joint defect can be identified and optimally treated directly impacts the success of any treatment protocol. Currently available orthopedic diagnostic methods are capable of detecting a limited number of specific and treatable defects. These techniques include X-Rays, MRI, discography, and physical exams of the patient. In addition, spinal kinematic studies such as flexion/extension X-rays are used to specifically detect whether or not a joint has dysfunctional motion. These methods have become widely available and broadly adopted into the practice of treating joint problems and addressing joint performance issues. However, currently available diagnostic techniques provide measurement data that is imprecise and often inconclusive which results in an inability to detect many types of pathologies or accurately assess pathologies that might be considered borderline. As a result, a significant number of patients having joint problems remain undiagnosed and untreated using current techniques, or worse are misdiagnosed and mistreated due to the poor clinical efficacy of these techniques.
For example, currently available techniques for conducting spinal kinematic studies are often unable to determine whether a joint dysfunction is a result of the internal joint structure per se, or whether the dysfunction is a result of, or significantly impacted by, the surrounding muscular tissue. Additionally, there are no reliable techniques for identifying soft tissue injury. Muscle guarding is a well established concept that is hypothesized to be highly prevalent among sufferers of joint pain, specifically that of the neck and back. In muscle guarding, a subject responds to chronic pain by immobilizing the painful area through involuntary muscle involvement. The ability to isolate different muscle groups is desirable to determine which muscle group or combination of groups, if any, could be contributing to, or responsible for, any joint dysfunction.
Additionally, the level of entrenchment of muscle guarding behavior cannot currently be determined. With respect to treatment decisions, the operative question in determining the level of “entrenchment” of any observed muscle guarding is to determine if the muscle guarding behavior is one which conservative methods of therapy could address through non-surgical therapy, or alternatively determining that the muscle guarding behavior so “entrenched” that such efforts would be futile and surgery should be considered.
In some instances, joint dysfunctions may not always present themselves in the movements traditionally measured during spinal kinematic studies such as flexion-extension and side-bending in either “full” non-weight-bearing or “full” weight-bearing planes of movement, which correspond to lying down and standing up postures respectively. Certain painful movements occur during joint rotation when the plane of rotation is somewhere between these two postures. Certain other painful movements only occur when the subject is rotating his or her spine while in a bent posture. In the case of vertebral motion in full weight-bearing postures, gravitational forces are relatively evenly distributed across the surface area of the vertebrae. However in postures where the subject is standing with his/her spine bent, gravitational forces are concentrated on the sections of the vertebrae located toward the direction of the bend. Detecting motion dysfunctions that occur only when in a standing bent posture requires the replication of joint motion in that specific bent posture in a controlled, repeatable, and measurable manner during examination.
Further, assuming that a system of measuring the surface motion of joints and the motion between internal joint structures that accounts for various types of muscle involvements would be possible, there would be a need for investigational data from controlled clinical trials to be collected across a broad population of subjects to afford for comparative analyses between subjects. Such a comparative analysis across a broad population of subjects would be necessary for the purpose of defining “normal” and “unhealthy” ranges of such measurements, which would in turn form the basis for the diagnostic interpretation of such measurements.
There have been significant technological innovations to the field of orthopedic interventions over the last few decades, specifically with the use of prosthetic and therapeutic devices to correct mechanical and structural defects of the bones and joints and to restore proper joint function. There have also been significant advances in the application of chiropractic and physical therapy approaches to correct muscle-, ligament-, and tendon-related defects. There has not however, been a corresponding improvement in the diagnostic methods used to identify proper candidates for these interventions. As a result, the potential impact and utility of the improvements in orthopedic intervention has been limited.
Imaging is the cornerstone of all modern orthopedic diagnostics. The vast majority of diagnostic performance innovations have focused on static images. Static images are a small number of images of a joint structure taken at different points in the joint's range of motion, with the subject remaining still in each position while the image is being captured. Static imaging studies have focused mainly on detecting structural changes to the bones and other internal joint structures. An example of the diagnostic application of static imaging studies is with the detection of spinal disc degeneration by the use of plain X-rays, MR images and discograms. However, these applications yield poor diagnostic performance with an unacceptably high proportion of testing events yielding either inconclusive or false positive/false negative diagnostic results (Lawrence, J. S. (1969) Annals of Rheumatic Diseases 28: 121-37; Waddell, G. (1998) The Back Pain Revolution. Edinburgh, Churchill Livingstone Ch2 p22; Carragee et al. (2006) Spine 31(5): 505-509, McGregor et al. (1998) J Bone Joint Surg (Br) 80-B: 1009-1013; Fujiwara et al. (2000(a)) Journal of Spinal Disorders 13: 444-50).
Purely qualitative methods for visualizing joint motion have been available for some time using cine-radiography (Jones, M. D. (1962) Archives of Surgery 85: 974-81). More recently, computer edge extraction of vertebral images from fluoroscopy has been used to improve this visualization for use in animations (Zheng et al. (2003) Medical Engineering and Physics 25: 171-179). These references do not, however, provide for any form of measurement or identification of objectively defined motion abnormalities, and therefore is of very limited diagnostic value other than in the detection of grossly and visibly obvious abnormalities that would be detectable using static image analysis methods. Without any quantitative or objective measurement parameters defined, it is impossible to utilize such approaches in comparative analyses across wide populations of subjects, which is required for the purpose of the producing definitive diagnostic interpretations of the results as being either “normal” or “unhealthy”. Further, there have been no diagnostically useful validations of qualitative motion patterns that are generally absent in non-sufferers but present in subjects suffering from known and specific joint functional derangements or symptoms, or vice versa.
A method for determining vertebral body positions using skin markers was developed (Bryant (1989) Spine 14(3): 258-65), but could only measure joint motion at skin positions and could not measure the motion of structures within the joint. There have been many examples skin marker based spine motion measurement that have all been similarly flawed.
Methods have been developed to measure changes to the position of vertebrae under different loads in dead subjects, whose removed spines were fused and had markers inserted into the vertebrae (Esses et al. (1996) Spine 21(6): 676-84). The motion of these markers was then measured in the presence of different kinds of loads on the vertebrae. This method is, however, inherently impractical for clinical diagnostic use. Other methods with living subjects have been able to obtain a high degree of accuracy in measuring the motion of internal joint structures by placing internal markers on the bones of subjects and digitally marking sets of static images (Johnsson et al. (1990) Spine 15: 347-50), a technique known as roentgen stereophotogrammetry analysis (RSA). However RSA requires the surgical implantation of these markers into subjects' internal joint structures, requires the use of two radiographic units simultaneously, and requires a highly complicated calibration process for every single test, and therefore is too invasive and too cumbersome a process for practicable clinical application.
Cine-radiography of uncontrolled weight-bearing motion (Harada et al (2000) Spine 25: 1932-7; Takavanagi et al. (2001) Spine 26(17): 1858-1865) has been used to provide a set of static images to which digital markers have been attached and transformed to give quantitative measurement of joint motion. Similar measurement of joint motion has been achieved using videofluoroscopy (Breen et al. (1989) Journal of Biomedical Engineering 11: 224-8; Cholewicki et al. (1991) Clinical Biomechanics 6: 73-8; Breen et al. (1993) European Journal of Physical Medicine and Rehabilitation 3(5): 182-90; Brydges et al. 1993). This method has also been used to study the effects on joint motion of weightlifting (Cholewicki, J. and S. M. McGill (1992) Journal of Biomechanics 25(1): 17-28). The prior art using this method involves a manual process in which internal joint structures are marked by hand with digital landmarks on digital image files of consecutive frames of videoflouroscopy recordings of a subject's joint motion. A computer then automatically determines the frame-to-frame displacement between such digital landmarks to derive quantitative measurements of the motion of joint structures (Lee et al. (2002) Spine 27(8): E215-20). Even more recently, this approach has been accomplished using an automatic registration process (Wong et al. (2006) Spine 31(4): 414-419) that eliminates the manual marking process and thus reduces the laboriousness of the previous processes. However both of these methods, as well as all of the other methods mentioned in this paragraph, studied the motion of joints based on the imaging of uncontrolled, weight-bearing body motion.
Using uncontrolled, weight-bearing motion to derive quantitative measurements of joint motion confounds the diagnostic interpretation of such measurements so as to render them diagnostically useless. The diagnostic interpretation of such measurements would normally be based on a comparative analysis of joint motion measurements across a wide population of subjects, and would strive to identify statistically significant differences in these measurements between “normal” and “unhealthy” subjects, such that any given subject can be classified as “normal” or “unhealthy” based on that subject's joint motion measurement values. For such purposes, it is necessary to reduce the background variability of measurements across tested subjects as much as possible, so that any observed difference between “normal” and “unhealthy” subjects can be definitively attributable to a specific condition. Not controlling the motion that is being studied introduces variability into these comparative analyses due to differences that exist across testing subjects with respect to each subject's individual range of motion, symmetry of motion, and regularity of motion. These differences affect the joint motion of each subject differently, and collectively serve to create wide variability among joint motion measurements across subjects. Controlling for these factors by ensuring a consistent, regular, and symmetric body part motion during diagnostic testing serves to minimize the effects of these factors on a subject's relevant joint motion measurements, thereby reducing the variability of such measurements across subjects and therefore increasing the likelihood that such measurements will yield useful diagnostic results.
In addition to failing to control motion during testing, not accounting for the involvement and effects of muscles that are acting when a subject moves under their own muscular force while in a weight-bearing stance further adds to this variability by introducing such inherently variable factors such as the subject's muscle strength, level of pain, involuntary contraction of opposing muscle groups, and neuro-muscular co-ordination. Taken together, all of these sources of variability serve to confound diagnostic conclusions based on comparative analyses by making the ranges of “normal” and those of “abnormal” difficult to distinguish from one another other in a statistically significant way. Such an inability to distinguish between “normal” and “unhealthy” subjects based on a specific diagnostic measurement renders such a measurement diagnostically useless, as has been the case heretofore in the prior art which has focused on measurements of uncontrolled joint motion measured in subjects in weight-bearing postures and moving their joints through the power of their own muscles and in an uncontrolled fashion.
U.S. Pat. No. 7,000,271 discloses a tilting table capable of some movement to keep an iso-center at a fixed position. U.S. Pat. No. 7,343,635 describes a multi-articulated tilting table which positions and supports a subject during examination and treatment. U.S. Pat. No. 7,502,641 to Breen discloses a device for controlling joint motion and minimizing the effects of muscle involvement in the joint motion being studied. This device minimizes variability among joint motion measurements across wide populations of subjects. As a result, comparative analyses of such measurements can be performed to determine statistical differences between the motion of “normal” and “unhealthy” subjects which in turn can provide a basis for determining the statistical confidence with which any given subject could be considered “normal” or “unhealthy” based solely on joint motion measurements.
U.S. Pat. No. 5,505,208 to Toomin et al. developed a method for measuring muscle dysfunction by means of collecting muscle activity measurements using electrodes in a pattern across a subject's back while having the subject perform a series of poses where measurements are made at static periods within the movement. These electromyographical readings of “unhealthy” subjects were then compared to those of a “normal” population so as to be able to identify those subjects with abnormal readings, however does not provide for a method to report the results as a degree of departure from an ideal reading, instead can only say whether the reading is “abnormal”. U.S. Pat. No. 6,280,395 added an additional advantage to this method for determining muscle dysfunction by using the same method, yet adding the ability to better normalize the data by employing a more accurate reading of the thickness of the adipose tissue and other general characteristics that might introduce variability into the readings, as well as the ability to quantify how abnormal a subject's electromyographical reading is as compared to a “normal” population.
Joint muscle activity has been evaluated using electromyography in combination with some type method or device to track the surface motion of the joint. In one study, visual landmarks were used to help the subject more consistently reproduce a tested motion so as to standardize the joint motion and eliminate variability. (Lariviere, C 2000) However, visual land marking methods to not yield as “standardized” a motion as can be achieved with motion that is mechanically controlled, and measurements of the motion of internal joint structures based on surface motion measurements are too variable to be of significant clinical utility.
Another study used electromyography in conjunction with the use of a goniometer, a device that measures the surface motion of external body parts so as to link the muscle activity signals with precise surface motion measurements. (Kaigle et al. (1998) Journal of Spinal Disorders 11(2): 163-174). This method however does not take into consideration the motion of internal joint structures such that a determination as to the specific cause of joint dysfunction cannot be evaluated.
Electromyographic measurements taken during weight-bearing joint motion, with simultaneous recording of the motion of the body part using goniometers and also with simultaneous recordings of the motion of internal joint structures through the tracking of surgically-implanted metal markers, has been used to correlate muscle activity with the motion of joints and internal joint structures (Kaigle, supra). However this approach studied joint motion that was uncontrolled and required an invasive surgical procedure to place the metal markers, and thus were neither useful nor feasible for clinical diagnostic application.
Electromyography has also been used in conjunction with a device that provides transient force perturbation so as to observe whether there is a difference between subjects with low back pain and those without low back pain to determine how their muscles respond to such a force. (Stokes, Fox et al. 2006) The objective was to determine whether there is an altered muscle activation pattern when using a ramped effort. This approach however does not address the issue of which discrete muscle group or groups might account for the difference between activation patterns in subjects with joint dysfunctions and those without. Furthermore, this method does not take into consideration the internal structural joint motions and thus provides an incomplete set of information upon which to draw diagnostic conclusions.